

As temperatures climb and the global population grows, the youngest and oldest among us are being exposed to billions more hours of unhealthy heat than in past decades.

Very young children (those under 1 year old) and older adults (over 65 years old) are more vulnerable to unhealthy levels of heat in part because they sweat less than others. Exposure to dangerous heat is increasing in the most vulnerable age groups It might surprise you that the United States is one of the most heat-vulnerable nations in the world, due to our relatively large urban population, high proportion of older adults, and high prevalence of chronic diseases such as diabetes. Nearly every nation in the world has become more vulnerable to heat over the last 30 years, as seen in the animated map below from the Lancet Countdown’s data visualization tool.

